1. Field of the Invention
The present invention relates to an adjustment module, and more particularly, to a voltage adjustment module used in a power supply device.
2. Description of the Related Art
Referring to FIG. 1, a conventional non-isolated direct current-to-direct current (DC-to-DC) converter 900 comprises a pulse width modulator (PWM) 910 and a power switch module 920. The DC-to-DC converter 900 outputs drive signals VG1, VG2 through the PWM 910, and respectively drives a first power switch PQ1 and a second power switch PQ2 in the power switch module 920 to turn on and off to thereby output a voltage PVout for supply to a back-end device (represented by impedance RL in FIG. 1).
However, the conventional PWM 910 is only able to receive a supply power (typically 5V or 12V), such that the drive signals VG1, VG2 output thereby are only able to use a voltage level equal to the supply voltage to drive the power switch module 920. For example, when the supply power is 5V, the drive signals VG1, VG2 drive the power switch module 920 with a voltage level of 5V. Therefore, when the DC-to-DC converter 900 is in a low current lout output state (i.e., high impedance RL), it has a relatively high conversion efficiency. However, when the DC-to-DC converter 900 is in a high current Iout output state (i.e., low impedance RL), the internal resistances of the first power switch PQ1 and the second power switch PQ2 when turned on become high to thereby cause excessive loss during conduction and the conversion efficiency of the DC-to-DC converter 900 to reduce.
At the same time, when the supply power is 12V, the drive signals VG1, VG2 drive the power switch module 920 using a voltage level of 12V. As a result, when the DC-to-DC converter 900 is in a high output current Iout state, the first power switch PQ1 and the second power switch PQ2 may have relatively low internal resistances when turned on. As a result, in this state, the conversion efficiency when the supply power is 12V is higher than the conversion efficiency when the supply power is 5V. However, when the DC-to-DC converter 900 is in a low output current Iout state, the first power switch PQ1 and the second power switch PQ2 are in a state driven by a 12V voltage level, and excessive power loss results during switching thereof, such that the conversion efficiency of the DC-to-DC converter 900 is reduced. Hence, the conventional DC-to-DC converter 900 is unable to exhibit good conversion efficiency when in both high output current Tout and low output current lout states.